The years when your age is 30-50 are the years of your 'Peak Effectiveness'. If you're going to achieve something, it will most likely be in that time.<p>The Millennials are in that age-zone. So they're naturally going to have an effect.
It's interesting to note that just by being slightly larger or smaller, a cohort can affect demand for all sorts of things, from college places to the job market, and starter homes.